In the previous article we looked at the majority of taxa included within the ‘plecotin’ group. As discussed therein, while there may be a clade of ‘core plecotins’, the traditional concept of the group might be paraphyletic. Some plecotins – Idionycteris in particular – might even be outside the clade that includes plecotins and all other vespertilionines. Here we look at a particularly interesting group of vesper bat species that might, or might not, be part of the ‘core plecotin’ clade: the desert long-eared bats (Otonycteris). What makes desert long-eared bats especially interesting is that, along with being desert-dwelling specialists (as you’d guess by the name), they’re ground-foraging gleaners, described as among the most predatory of Palaearctic bats, and well able to prey regularly on scorpions, solifugids and perhaps even on lizards. They also look really, really scary. [Adjacent photo by Charlotte Roemer, from wikipedia].
Occurring throughout arid north Africa and the Arabian Peninsula, and also in central Asia as far east as Pakistan, desert long-eared bats occur in true desert habitats as well as in semi-deserts and oases. They roost in rocky crevices and sometimes in buildings. Like other plecotins, they have proportionally large ears (up to 40 mm long: that’s about half of their head + body length). In contrast to Plecotus and similar taxa, their ears are not connected at their bases by a band of skin. These are large vesper bats, with a mass of 18-30 g and a wingspan of 35-40 cm. [Photo below – showing a female O. hemprichi captured in Sinai, Egypt – by P. Benda, from Benda et al. (2008)].

During recent decades most authors have classified all Otonycteris populations as belonging to a single, highly variable species (O. hemprichi) sometimes known as Hemprich’s long-eared bat*. However, variations in skull shape have led to the suggestion that this might actually represent a species complex, or at least deserve splitting into several subspecies. Benda & Gvoždík (2010) examined both morphology and genetics and found that the desert long-eared bats of Africa and the Middle East could be readily distinguished from the central Asian ones, and they concluded that the two should be regarded as separate species. The central Asian species (O. leucophaea) could, in turn, be split into three subspecies.

* Incorrectly spelt ‘Hempriche’s long-eared bat’ in one or two books. The species name is spelt hemprichi by some authors, and hemprichii by others.

Taking scorpion stings to the face and other such acts of badassery

The eyes in these bats always look relatively large, and they have an alert, aggressive demeanour (I’m basing all this on photos: I’ve never knowingly* seen a live one!). Combined with a pale coat, semi-translucent wing membranes, large ears and impressive teeth, this look makes these bats superficially resemble the much larger, predatory megadermatids (false vampires and ghost bats). Indeed, their low aspect ratio wings and low wing loading led to suggestions that they’re most likely ground-feeding gleaners – possibly of small vertebrates (Norberg & Fenton 1988) – long before this behaviour was properly documented. Observations made since show that they land briefly (2-5 seconds) on the ground to catch prey before chewing nosily, taking off and eating the prey in flight: beetle larvae have been found as stomach contents in some studies, demonstrating a ground-gleaning habit beyond doubt. Holderied et al. (2010) confirmed that, like megadermatids, Otonycteris uses prey-generated noises when hunting, sometimes detecting scorpions via their walking sounds. These bats do use quiet echolocation as well.

* I did see many bats while in Morocco, but was never able to identify them.

Desert long-eared bat diet seems to mostly consist of such terrestrial arthropods as scorpions, solifugids, beetles, cockroaches and crickets, making them “the strongest predator among Palearctic insectivorous bats” (Arlettaz et al. 1995, p. 875). They drop right on to their scorpion prey and may be repeatedly stung on the body and face while subduing them: amazingly, this seems to have no effect and the bats display no evidence whatsoever of selecting scorpions based on their size or toxicity (Holderied et al. 2010). The conclusion must be that they’re generalist predators of scorpions as a whole. They eat the whole scorpion – sting and all – and more than 70% of their droppings are made up of scorpion remains at some times of the year.

The idea of a predatory vesper bat that attacks, kills and consumes venomous scorpions as well as solifugids and (perhaps) lizards is undeniably badass even though – granted – these prey animals might be just a few centimetres long (the gecko in question is 11 cm long) [below is an image I found in the Tet Zoo archives: it depicts the age-old battle between desert long-eared bats and scorpions. For a larger version, look at the Tet Zoo facebook page]. Arlettaz et al. (1995) found scorpions, solifugids and grasshoppers to form the bulk of the desert long-eared bat diet [see their diagram of diet broken down taxonomically, above], but Benda et al. (2008) reported scarabaeid beetles to be more important. However, the data in the latter study came from an oasis where human impact might influence the bat’s foraging habits and choice of prey.

Roaming all over the cladogram

It has proved difficult to classify desert long-eared bats, and don’t assume that they’ve always been recovered close to (or within) ‘core plecotins’; in fact, several radically different phylogenetic hypotheses have been published. As we saw in the previous article, ‘core plecotins’ have a cute, short-faced look whereas Otonycteris looks rather more like snarling demon from hell. Based on this most empirical and scientific rigorous of evaluations, I think it can certainly be doubted that Otonycteris is a plecotin. Koopman & Jones (1970) regarded Otonycteris as a nycticein, close to evening bats (Nycticeius), little yellow bats or rhogeëssa bats (Rhogeesa) and house bats (Scotophilus), but karyotypic evidence later suggested an affinity with plecotins (e.g., Qumsiyeh & Bickham 1993).

Hoofer & van den Bussche (2001) found Otonycteris to be well removed from a plecotin clade, and to instead be the sister-taxon to an Antrozous (pallid bats) + Rhogeesa clade. In other words, they found Otonycteris to be part of Antrozoini, a clade we haven’t yet discussed in this series (don’t worry, it’s coming soon). This is really interesting given that pallid bats at least are notable for their robust jaws and teeth and Otonycteris-like habit of ground-gleaning and preying on (relatively) large animals.

Since then, a larger analysis has put Otonycteris back with the plecotins (Roehrs et al. 2010): sometimes within ‘core plecotins’ and sometimes within a Plecotini + Lasiurini clade. I think it’s safe to say that the phylogenetic affinities of these fascinating predatory bats have yet to be resolved, though an affinity with plecotins in the broad sense does seem most widely supported.

So… that’s all of the plecotin or plecotin-like bats out of the way. Next: hairy-tailed bats or hoary bats. For previous Tet Zoo articles in the vesper bats series, see…

I’d snarl too if some git held me in that uncomfortable manner. I’ve worked with these bats in a rehab setting and found them calm but determined. Only one even attempted to bite and that was while having a wound cleaned. They are a wonder of nature – as are all bats.

These things look rather similar to pallid bats – roosting habits, appearance in flight, etc. When I was working at a snake farm in Turkmenistan as a kid, we had a small roost in the wall of one of the buildings, and a night roost under a roof edge nearby. On a few occasions when I saw them eating prey it was large spiders, probably wolf spiders or something like that.

They do indeed look superficially similar to pallid bats (Antrozous). So, it’s interesting that – as can you see in the discussion (and on the cladogram) above – some workers have suggested an affinity between the two. This is mostly regarded as convergence, however, and most evidence puts Otonycteris among the plecotins. I saw large, pale bats in the Sahara, but they were social, fast-flying and also very noisy, so I don’t think they were desert long-eared bats. Also had close encounters with several solifugids…

Having taken a scorpion sting only once in my life,( and that to the foot ) I’ll just say these are clearly tough little fellows. I just wish there was a local variety that
might develop a taste for wasps. ( which have stung me in the face. twice. ) @Robert(comment 6) The BLack Scorpion could have only been improved by the addition
of giant, scorpion-eating bats.

In all seriousness, I have a generic bat-related question: Compared to pterosaurs and birds, bats seem to have pathetically weak arms and legs. I’m looking at that second picture and thinking, “does that thing even have muscles in its limbs? I can see its bones!” Is it just that particular bat, or have bats evolved some other method of powering their flight than pterosaurs and birds? Is it all in the shoulders–which are conveniently covered in thick fur?

@14 Zach: Actually, birds have most of their muscles in their chests too. There’s a couple of advantages: locate the most of the mass around a center of mass, but more importantly, it minimizes weight, because the shoulder muscles don’t have to move heavy arm muscles that are out on that arm.

Another thing is that bat bones aren’t hollow, which imposes a bigger weight penalty on them.